Germanene termination of Ge${_2}$Pt crystals on Ge(110)

TL;DR

This study demonstrates the formation of a germanene-like layer on Ge2Pt nanocrystals grown on Ge(110), revealing a honeycomb structure with properties similar to predicted germanene.

Contribution

It provides experimental evidence for germanene formation on Ge2Pt nanocrystals, advancing understanding of 2D germanene layers on metal-semiconductor interfaces.

Findings

Honeycomb structure with 2.5 Å nearest-neighbor distance.

Outer layer is more metallic than underlying layers.

Proposed layer is a germanene-like 2D material.

Abstract

We have investigated the growth of Pt on Ge(110) using scanning tunneling microscopy and spectroscopy. The deposition of several monolayers of Pt on Ge(110) followed by annealing at 1100 K results in the formation of three-dimensional metallic Pt-Ge nanocrystals. The outermost layer of these crystals exhibits a honeycomb structure. The honeycomb structure is composed of two hexagonal sub-lattices that are displaced vertically by 0.2 {\AA} with respect to each other. The nearest-neighbor distance of the atoms in the honeycomb lattice is 2.5${\pm}$0.1 {\AA}, i.e. very close to the predicted nearest-neighbor distance in germanene (2.4 {\AA}). Scanning tunneling spectroscopy reveals that the atomic layer underneath the honeycomb layer is more metallic than the honeycomb layer itself. These observations are in line with a model recently proposed for metal di-(silicides/)germanides: a hexagonal crystal with metal layers separated by semiconductor layers with a honeycomb lattice. Based on our observations we propose that the outermost layer of the Ge2Pt nanocrystal is a germanene layer.